Apparatus for producing coated fabrics



April 1952 c. s. FRANCIS, JR 5 2,593,553

APPARATUS FOR PRODUCING COATED FABRICS Filed May 31, 1946 Patented Apr.22, 1952 APPARATUS FOR PRODUCING COATED FABRICS Carleton S. Francis,Jr., West Harwich, Mass, assignor, by mesne assignments, to AmericanViscose Corporation, Wilmington, Del., a corporation of DelawareApplication May 31, 1946, Serial No. 673,685

This invention relates in general to coating waterproof fabrics and inparticular to a process and apparatus for producing such fabrics by useof thermoplastic transfers and includes correlated improvements designedto enhance the appearance, improve the strength and extend the use ofcoated fabrics.

In the production of mountain tents, ponchos, rain coats, andlight-Weight tarpaulins, particularly for use by aircraft personnel andparatroops, it is essential that both the total weight and the thicknessof such sheet materials be maintained at an absolute minimum, However,such coated materials must meet the following stringent specifications:

(a) They must be extremely light in weight;

(b) They must be waterproof and water-repellent;

They must not become tacky when folded and stored under pressure, evenin the tropics at temperatures up to 125 F.;

(d) They must not become brittle or inflexible at the lowesttemperatures experienced in the arctic regions;

(6) They must be impermeable and proof against the effects of both watervapor and gases.

It has been found that conventional methods of coating fabrics will notmeet all of the above stringent requirements. In particular, it hasstrength and stretch of the fabric are all important factors. increasethese factors by increasing the yarn count of the fabric, it has beenfound that after 2 Claims. (Cl. 15437) coated fabrics with a thincontinuous impervious been found that the tear resistance, tensile.

When an attempt is made to a certain yarn count, further increases inthe yarn count actually cause a decrease in the tear resistance and alsoproduce a very marked decrease in the stretch. These decreases in tearresistance and stretch are further augmented when the fabrics are coatedby conventional processes involving the application of flowablecompositions to the fabric because such prior processes invariablyresult in impregnation of the'yarns to a substantial extent. It has beenfound that when the yarns are impregnated, they are stiffened and theyare thus unable to adjust themselves to stretching forces, and ifdistorted by tension, such impregnated yarns do not recover to anymaterial extent but remain stretched. It is obvious that increasing theyarn count and impregnating the yarns with the coating composition bothtend to increase the total weight of the coated fabric.

Accordingly, it is a general object of the present inventionto overcomepresent disadvantages residing in prior coated fabrics while providingcoating.

Another general object of the invention is to provide a light weightfabric which will have 1 high tear resistance, high tensile strength anda substantial stretch while exhibiting a material recovery after beingstretched.

A specific object of the present invention is to provide a method ofcoating fabrics without impregnating the yarns thereof.

A further specific object is to provide an open mesh textile fabric witha thin continuous nonselfsupporting impervious coating.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

According to the present invention, an open mesh textile fabric iscoated Without impregnating the yarns thereof by applying to each sideof the fabric a thin continuous nonselfsupporting impervious film of anorganic thermoplastic material supported on a temporary backing to whichthe film exhibits no permanent adhesion, applying heat and pressure tothe assembled sheet material to cause the films to adhere to thesurfaces of opposite outer sides of the yarns and to fuse to each otherin the spaces between the yarns, the films and inner sides of the yarnsthereby defining spaces between them, and preferably after cooling thearticle, stripping the temporary backing sheets from the coated fabric.The coated fabric thereby produced is characterized by superiortear-resistance and tensile strength.

The expression open mesh fabric as used in the specification and in theappended claims 'is used in its conventional meaning in the textile art,that is, a fabric having discrete and substantial spaces between theyarns in such a fabric.

For a more complete understanding of the nature and objects of thepresent invention, reference should be had to the accompanying drawingin which:

Figure 1 is a diagrammatical representation in side elevation of meansfor carrying out one embodiment of the process of the invention;

Figure 2 is a diagrammatical representation in side elevation of asecond embodiment of means for carrying out the process of theinvention;

Figure 3 is a perspective view of one embodiment of the fabric of theinvention;

Figure 4 is a cross-section of the fabric illustrated in Figure 3.

The invention is applicable to the coating of open mesh fabrics as aclass regardless of the method of their manufacture.

Thus, the open mesh fabrics may be formed by weaving, knitting, netting,crocheting, and the like.

Some common varieties of open mesh fabrics are, for example, scrim,cheesecloth, bobinet, and crinoline. It is to be understood that thefabrics may be formed of natural or artificial textile fibres andmixtures thereof. Improved anchorage of the coating to the yarns can beobtained if the yarns comprise organic thermoplastic fibres which arerendered tacky at the temperature at which the coating is applied.Suitable thermoplastic fibres may be formed from thermoplastic cellulosederivatives, thermoplastic synthetic resins, and compatible mixtures ofthese materials in accordance with the invention disclosed in my U. S.Patent No. 2,253,000.

The backing sheet The backing may be a flexible self-supporting filmformed of any film-forming organic material which is solid at roomtemperature but which has a softening point preferably above about 160C. but, in general, between about 100 C. and about 300 C., provided itsthermal softening point is above the thermal tacking point of thetransfer film employed.

The backing sheet should have a smooth, nonfibrous surface to which thetransfer film exhibits no permanent adhesion. Thus, the choice of thebacking sheet depends on the transfer film used.

Backing sheets which are operative in this invention include thefollowing classes of materials:

(a) Sheets formed in whole of or surfaced with a nonfibrous hydrophilicfilm-forming material such, for example as regenerated cellulose,alkali-soluble water-insoluble cellulose ethers, gelatine, casein,denitrated nitrocellulose deacetylated chitin, zein, and the like. Thus,the backing sheet may comprise a homogeneous film formed of one of suchmaterials or a layer of fibrous material such as paper, felt, or fabriccoated with such hydrophilic materials. All such backing sheets shouldhave a smooth, nonfibrous and nonthermoplastic surface which exhibits nopermanent adhesion to the transfer film.

(b) Sheets formed in whole of or surfaced with a hydrophobicthermoplastic or thermosetting composition, which has a thermalsoftening point higher than the thermal tacking point of the transferfilm. This embodiment of the backing sheet comprises preferably a sheetof paper or fabric coated with a thermosetting resin in the infusiblenonthermoplastic state. For such resins there may be used thethermosetting resins as a class, such as the resins employed in thetransfer film. It is essential that the transfer film show no permanentadhesion to the backing sheet or the coating thereon and whether it beformed of a thermoplastic or thermosetting material that it may bereadily stripped therefrom after transfer to the surface being coated.

Sheets, films, or endless bands, or a drum of polished metal, or metalfoil which is smooth, nonfibrous and nonthermoplastic under theconditions of temperature and pressure may be used in the transferoperation. The composition used for the production of the thermoplastictransfer film may, for example, be applied to a moving metallic band atone point and the solvent evaporated or the composition hardened bycooling. The film thus formed is preferably preheated and thentransferred from the metal support to the article to be coated at apoint spaced from the point of application of the composition to theband.

The transfer film For the thermoplastic transfer film which istemporarily applied to the backing sheet, there may be used anythermoplastic film-forming material, including thermoplastic cellulosederivatives as a class, thermoplastic synthetic resins as a class andthermosetting resins as a class while in a thermoplastic incompletelypolymerized state.

Thermoplastic resins Polyvinyl chloride Polyvinylidene chloridePolystyrene Copolymers of vinyl chloride and vinyl acetate Copolymers ofmethyl methacrylate and vinyl chloride Polyvinyl butyral Polyvinylacetal Polymethyl methacrylate Polymethyl acrylate PolyethylenePolyamides Coumarone-indene with rubber Oil-modified and unmodifiedalkyd resins (prepared from dihydroxy alcohols and dicarboxylic acids)Phenol-formaldehyde resins (prepared from phenols having only tworeactive positions) Polytetrafluoroethylene Polyvinyl alcoholThermoplastic cellulose compounds Cellulose acetate Cellulose acetatebutyrate Cellulose acetate propionate Cellulose propionate Benzylcellulose Ethyl cellulose Butyl cellulose Hydroxy ethyl celluloseThermosetting resins in a thermoplastic stage Urea-formaldehydeMelamine-formaldehyde Aniline-formaldehyde Phenol-formaldehyde (phenolshaving three reactive positions) Phenol-furfural Unsaturated polyestersPolyallyl alcohol and derivatives Protein-formaldehyde resins:casein-formaldehyde shellac-formaldehyde Alkyd resins (prepared frompolyhydric alcohols and polycarboxylic acids) Urea alcohol etherformaldehyde Mixtures of thermoplastic and thermosetting resinsPolyvinyl chloride and urea-formaldehyde-butanol ether Polyvinylchloride and phenol-formaldehyde Polymethylmethacrylate andurea-formaldehyde Polystyrene and alkyd Coumarone-indene and alkydpolyvinyl acetal and melamine-formaldehyde Polyvinyl butyral andurea-formaldehyde Liquid resin-forming ingredients Allyl alcohol Allylbromide Furfuryl alcohol Vinyl alcohol Liquid unsaturated hydrocarbonsOctylenes Coumarone Allyl chloride Furfural Acrylic acid esters IndeneEthylenic hydrocarbons Heptylenes Higher dienes Methylol ureaDicarboxylic acid esters of allyl alcohol The transfer film may alsocontain suitable plasticizers, moistureproofing agents, .water proofingagents, fireproofing agents, pigments, dyestuffs, and other materials asdesired. The plasticizer may be either volatile or nonvolatile.

The transfer film may be applied to the backing film by any suitablemeans. The transfer film composition, if liquid, may be coated upon thebacking sheet and then polymerized by heating to form a tackythermoplastic film. If solid, it maybe dissolved in a volatile solventwhich is a nonsolvent for the backing film, or the coating thereon, ifany, applied to the backing and dried at a temperature below thesoftenin point of the backing film. The transfer film material whensolid may also be melted and applied in a molten condition to thebacking film whenever the softening of the backing film is higher thanthe melting point of the transfer film material. Finally, the transferfilm material may be softened by heating "or by admixture with a solventto form a plastic mass which may then be calendered on to the surface ofthe plastic backing film, after which the calendered film is cooled orthe residual solvent evaporated.

Regardless of the method selected, it is apparent that the transfer filmmust not permanently adhere to the backing sheet.

Of the various thermoplastic or thermosetting materials which may beemployed for the transfer film, the synthetic elastomers as a class arepreferred over all other materials. Thin films formed of the syntheticelastomer have the property of stretching and recovering after stretch.This permits the finished product to be subjected to substantial stressand strain without permanent distortion or without permanent change indimension, since after the stress is removed the synthetic elastomerfilm causes the fabric to return to its original structure and shape.Further, the synthetic elastomers are superior to the other film-formingmaterials in their resistance to oils, greases, water vapor, and alsoexhibit a superior resistance to abrasion. The fact that the yarns ofthe fabric are not impregnated with the film permits the yarns also torecover their original shape after stress.

It is preferred to employ non-self-supporting films which are normallyless than one mil thick, since these films provide substantially thesame degree of imperviousness and protection as aself-supporting filmwhile possessing the advantages of lighter weight and lower cost; More'-over, mats and webs having a non-self-supporting film adhered to onesurface drape and are more flexible.

have better 6: The coating operation In producing the coated fabric ofthe invention, the transfer film supported upon the temporary backingsheet is adhered to the fabric to be coated by pressure.

The transfer film will preferably be in a tacky state at the timepressure is applied when contacting the fabric. This may be accomplishedby. (1) preheating the transfer film where the film is formed of a solidresin or cellulose derivative, or (2) where the film has been formed of,a liquid resin arresting the polymerization while the resin is stillin atacky state, or, (3) contacting the surface of the film briefly with asolvent by passing it over a kissing roll or brush. By procedures (2)and (3) the use of heat during lamination is made unnecessary.

Where heat is employed to render the trans: fer film tacky, the exacttemperature will, of course, depend upon the thermal tacking point ofthe transfer film. It will, however, be between the thermal tackingtemperature and within about C. higher than that temperature. In anyevent, it must not be so high that the film becomes fluid and fiowable;likewise, the film must not have a viscosity so low that impregnation ofthe fibers to a substantial extent occurs. Generally, the temperaturewill be between C. and200 0., the above conditions being met.

The pressure employed during lamination should be between about 25 and300 pounds per square inch, preferably between 50 and pounds per squareinch. It must be regulated carefully and preferably should be as low aspossible so as to prevent forcing the surface fibers of the fabricthrough the film. In the preferred finished product, the film should besubstantially as thick where it contacts the fibers as where it spansthe fibers.

There is shown in Fig. 1 one embodiment of suitable means for carryingout the invention in which backing sheets Hl carrying a transfer film Hon one surface are fed between the assembly rolls 13 so as to enclose aweb l2 of open mesh fabric supplied from the roll 9. The assembledsheets are then passed around the heated drum l4, being pressed againstthe drum by means of the blanket I5 which travels about the pressurerolls l6 and the tension rolls ll. Heat and pressure applied by the druml4 and blanket l 5 cause the transfer film to adhere to the yarns andfuse together between the yarns in the meshes. The stripping of thebacking sheets from the product is facilitated if the composite sheetmaterial is 1 cooled prior to stripping, for example, by passing thecomposite sheet material through the cooling chamber l8. The backingsheets are stripped from the coated fabric by passing around thestripping rolls 20. The backing sheets id and. the seated fabric l9 maybe wound up separately.

In Fig. 2 there is shown a second embodiment of means for carrying outthe process when it is desired to use self-supporting unbackedthermoplastic film. In this case the fabric i2 is led through the guiderolls I3 between two self-supporting thermoplastic films ii and theassembled sheets preheated in the chamber 2! after which they passthrough the nip of the heated calendar rolls 22 whereupon thethermoplastic films are adhered to the yarns and fused together in themeshes. To prevent the unbacked thermoplastic films from adhering to thesurface of the calendar rolls 22, these rolls may be covered with a,sheet of smooth hydrophilic material to which the thermoplastic filmsshow no tendency for 7. permanent adhesion such, for example, as webs 23of cellophane, gelatine, casein, alkali-soluble water-insolublecellulose ethers, and the like.

One embodiment of the product produced by this process is illustrated inFigs. 3 and 4 in which it is noted that the yarns 24 of the fabric areenclosed between the two transfer films l I although the yarns are notimpregnated by the material of the transfer film. It should also benoted that the two transfer films are fused together in the spaces 25 ormeshes between the yarns 24. The two coating films are adhered to theopposite outer surfaces of. the yarns, the films and inner sides of theyarns thereby defining spaces 26 between them. Accordingly, the fibresin the individual yarns are relatively free to move upon each other. Onthe other hand, the fusion of the films between the yarns permits thefabric to be stretched and distorted but also promotes the promptrecovery of the fabric and stabilize its dimensions.

It is to be understood that many variations and alternatives arepossible in the article and process of the invention. If desired, thetransfer film which is applied to the one side may be dissimilar inchemical composition, color, thickness and other characteristics fromthe transfer film which is applied to the other side. For example, formilitary ponchos and tents to be used in the arctic, the film on oneside is preferably pigmented or colored white while the film on theother side may be colored or pigmented olive drab. Also, the transferfilm on one side may comprise an acid-curing thermosetting resin and alatent acid catalyst so that after the fabric is coated, the fabric maybe subjected to curing conditions to convert the resin to theheat-hardened infuslbl state, while the thermoplastic coating on theother side remains uncured, thus retaining substantial flexibility inthe coated fabric. It is also possible, if desired, to apply athermoplastic cellulose derivative file on one side of the fabric and athermoplastic or thermosetting resin film on the other side.

By way of illustration but not by way of limiting the invention, therewill be given the .following specific examples:

EXAMPLE I A cotton scrim having 16 yarns to the inch is coated on bothsides with a film of a thermoplastic cellulose acetate butyrateplasticized with dibutyl phthalate. Each of the transfer films has athickness of from 0.0005 to 0.001 inch. The coated fabric thus producedhas an overall thickness much less than coated scrim produced by priorprocesses, has a tear resistance and tensile strength substantiallygreater than prior cotton scrim of the same yarn count, and the presentproduct also exhibits a recovery from stretching and dimensionalstability much greater than the same fabric coated by prior methods.

EXAMPLE II A cotton scrim having a leno weave and comprising 8 yarns tothe inch is coated on both sides with a preformed film comprising athermoplastic copolymer of vinyl chloride and vinyl acetate plasticizedwith a mixture of 50% methyl cellosolve acetyl ricinoleate and 50%tricresyl phosphate. The two films are fused together in the meshes bysubjecting the composite fabric to a temperature of 130 C. at 200 lbs.pressure per square inch for-l seconds.

EXAMPLE III 3 To a nylon marquisette fabric there is applied onjeachsidea film having a thickness of .001", the film comprising 70% of anacetone-soluble fusible phenol-formaldehyde resin, 20% of polyvinylbutyral resin'and 10% of dibutyl sebacate as a plasticizer. The filmsare first formed on a sheet of cellophane as a temporary backing, bothfilms being applied to the fabric simultaneously at a temperature of 150C. and 200 lbs. pressure to cause the films to fuse together in themeshes between the yarns; however, the film is continuous over the yarnsand does not substantially penetrate the yarns. The fabric will haveextremely light weight, high tensile strength and a remarkable abilityto recover its shape and dimensions after distortion. The fabric isideal for raincoats or ponchos.

EXAMPLE IV The process of Example III is repeated but to the compositionof the thermoplastic film there is added /z% of chloracetic acid as acuring catalyst for the thermosetting phenol resin and, after transfer,the composite fabric is heated to C. for one-half hour to cure thethermosetting resin and render the film non-thermoplastic. The fabriccan be used for making containers for water or gasoline.

EXAMPLE V A tear resistant Waterproof fabric is produced as follows: Asolution is prepared containing 260 parts of vinyl acetate polymer, 30parts methylmethacrylate resin, and 9 parts dibutyl phthalate in asuitable solvent. Films having a thickness of .005" are formed on atemporary backing sheet comprising paper coated with thermosettingurea-formaldehyde resin in the heat-hardened condition, and such filmsare transferred at a temperature of C. and 300 lbs. pressure to enclosea single thickness of nylon marquisette fabric, the films beingcontinuous over the yarns but fused together in the meshes. The film isextremely flexible and elastic and capable of following the expansionand contraction of the fabric Without rupture of the film.

EXAMPLE VI The process of Example V is repeated except that the fabricis enclosed between two films of Neoprene having a thickness of .001",the films being bonded together by heat and pressure in the meshes. Thisfabric will have a superior elasticity, a more complete regain of shapeand dimension and a higher abrasion resistance than the fabrics producedaccording to the other examples. The fabric is suitable for use inmaking flexible, collapsible containers for gasoline.

EXAMPLE VII A composition comprising a mixture of polyvinyl butyral, aphenol-formaldehyde resin in a thermoplastic state and olive drabpigments was formed into a transfer film upon a backing sheet of smoothinfusible urea-formaldehyde resin-coated paper. This transfer film wasadhered to an open mesh cotton marquisette fabric at a temperature of100 C. and a pressure of 35 lbs. per square inch. The weight of coatingper square yard of coated fabric was found to be 3.22 ounces.

Another section of the same cotton marquisette fabric was coated by thedoctor blade method using the same coating composition, dissolved infibrous layer, means for concurrently cooling the films and both sidesof the fibrous layer, and means for concurrently drawing the backingsheets in substantially opposite directions away from the films,concurrently stripping both backing sheets from the films and windingthe backing sheets in rolls while supporting the asq s tte fabric in aseries of tests. The 1'6- sembled films and fibrous layer from bothsides sults of the test-s were as follows: in a region adjacent theregion in which the Fabric Coated with Fabric Coated the Doctor BladewithaTransier figjfg ethod Film Hydrostatic Pressure Tests The sampleshowed Leakage at a awaterproofrating haght of in tests. The macms.terial held a water column at a. height 0150 cmsforlhour withoutleakage. Tear Resistance: (Strip Tear Method Federal SpecificationCCC-T-19la) Warp Across Filling lbs.- 2.5 3.5 6 Filling Across Warp lbs2.5 4.5 4-16 Average Tensile Strength: (0 C CTl9la Grab Method)- Warp(Length) .lbs 65.0 61.5 42.3 Filling (Widt lbs 70.0 73.5 48.3 BurstingStrength: (Mullbs 142.5 138.5 142.3

len Tester). Weight Per Square Yard.. ozs 10.38 4.20 0.98

The fabric was conditioned for four hours in an atmosphere of 65%relative humidity at 70 degrees Fahrenheit temperature before testing.

Thus, the coated fabric of the invention, despite the smaller weight ofcoating material employed, was found to have superior tear resistancewhile the tensile and bursting strength was also excellent. The degreeof imperviousness compared with the weight of the coating employed wasquite good, nearly the same degree of imperviousness being obtained withapproximately /3 the weight of coating.

These improved properties are believed the result of the freedom of theyarns to move upon each other in the coated fabric. In a fabric coatedby the doctor blade method the individual yarns of the coated fabric areheld together by the coating composition. In the fabric of the presentinvention the yarns are confined in pockets, the sides of the yarnsbeing free of coating film, thus materially increasing the amountofmovement possible by each yarn.

Many variations can be made in the process and apparatus withouttranscending the scope of the invention. For example, instead ofapplying the two thermoplastic films simultaneously to the singlethickness of fabric, these films may be applied in sequence. Theapparatus of Fig. 1 may be modified so that one of the films l I,supported on the backing sheet i0, is applied to the fabric I4 andbefore stripping off the backing sheet, a second film supported onanother backing sheet is applied to the other side of the fabric byinterposing heated calender rolls between the drum l4 and the coolingchamber [8, thereafter both backing sheets may be stripped from thefilms.

Having described my invention, what I claim is new and desire to secureby Letters Patent is:

1. Means for applying thin films of coating material to both sides of afabric layer comprising means for directing and concurrentlypositioninga fibrous layer between and in contact with two films ofthermoplastic coating material temporarily supported on backing sheets,means for uniformly subjecting the assembled films and fibrous layer toheat and pressure throughout their area to adhere the films to the n. Oi

backing sheets are stripped comprising a pair of stripping rollsengaging both of the backing sheets.

2. Means for applying thin films of coating material to both sides of afabric layer comprising means for concurrently positioning thin films ofthermoplastic coating material temporarily supported on backing sheets,on both sides of a fabric layer, means for uniformly subjecting theassembled films and fibrous layer to heat and pressure throughout theirarea to adhere the films to the fibrous layer, means for cooling theassembled films and fibrous layer, and means for concurrently drawingthe backing sheets in substantially opposite directions away from thefilms, concurrently stripping both backing sheets from the films, andwinding the backing sheets in rolls comprising a pair of stripping rollsengaging both of the backing sheets.

CARLETON S. FRANCIS, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,361,970 Dickey Dec. 14, 19201,519,239 Clay Dec. 16, 1924 1,956,545 Schrader et al. Apr. 24, 19341,994,697 Eichengrun Mar. 19, 1935 2,299,066 Berger Oct. 20, 19422,353,717 Francis et al. June 18, 1944 2,407,549 Gurwick Sept. 10, 19462,434,541 Bierer Jan. 13, 1948 2,442,443 Swallow June 1, 1948 2,460,571Chaifee Feb. 1, 1949 2,485,725 Francis Oct. 25, 1949 2,496,911 GreenFeb. 7, 1950 2,528,168 Paulsen Oct. 31, 1950 2,556,078 Francis June 5,1951 FOREIGN PATENTS Number Country Date 6,769 Great Britain 1893 4,959Great Britain 1910

